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Author Topic: MAF and Injector Scaling  (Read 92781 times)
Rick
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« Reply #45 on: November 25, 2010, 04:30:26 PM »

I'm on a stock MAF, with 630cc injectors but not sure what make they are as i didn't fit them.  Latency's are stock m box, i rescaled them to very similar to what Tony did and they are very good.  No misfires detected but there is a slight unevenness to the idle when the AC compressor is off.

Rick
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Tony@NefMoto
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2001.5 Audi S4 Stage 3


« Reply #46 on: November 29, 2010, 06:42:06 PM »

Hammersword reminded me that a better way to correct the idle misfires is with map FKKVS. This map allows you to correct injection time at different RPM and requested injection time.

He recommended reducing the injection time requested at low RPM and low requested injection time.
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Rick
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« Reply #47 on: December 04, 2010, 12:16:01 PM »

Tony,

surely your fuel trims would have the same effect?  You will always arrive at the same pw due to closed loop operation. 

However, changing torque reserve i.e. idle ignition angle will have an effect on idle quality.

RIck
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Jason
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« Reply #48 on: December 04, 2010, 04:41:37 PM »

In my experience too much idle timing advance can affect the O2s causing fuel trims to go excessively rich.  Too much idle timing will also result in higher NOx - something to consider if you have to pass a sniffer test.
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Tony@NefMoto
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« Reply #49 on: December 07, 2010, 10:10:45 PM »

surely your fuel trims would have the same effect?  You will always arrive at the same pw due to closed loop operation. 

The fuel trims effect fueling at all RPMs and load. The injection time for idle with the 630cc injectors only needs to be offset at low RPM and load.
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Rick
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« Reply #50 on: December 08, 2010, 07:42:49 AM »

LTFT's have two independant areas of adjustment don't they?  Idle and part throttle?

Regardless, my trims are within 1% now.  Reducing the idle timing by increasing idle torque reserve slightly does smooth out the idle very nicely. 

Rick
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Tony@NefMoto
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« Reply #51 on: December 14, 2010, 03:16:14 PM »

There are separate idle and part throttle long term fuel trims.
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wickster
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« Reply #52 on: December 15, 2010, 08:10:55 AM »

Just to let everyone know what I have been doing. My S4 has K04 turbos, Siemens 630cc injectors, stock MAF. I started with a stock tune that had the fuel injector scale corrected for the larger injectors. I then did numerous 10 to 20 minute test drives giving the car time to learn the response of the new fuel injectors. During the drive I would try to have idle, part load, and WOT, and multiple types of driving types. After each test drive I would read the long term idle fuel trim and the long term partial load fuel trim. Using those trim numbers I would adjust the fuel injector scaling and fuel injector latency map.

The long term partial load fuel trim is a percentage correction of the reference load for fuel injection. So if the long term partial load fuel trim is 5%, that means the car is scaling up the load by 5% to make the car run richer. The fuel injector scale is in (ms injection time / % load). So to adjust for the car needing to add 5% fuel to run at the correct AFR, I would then scale up the fuel injector scale by 5%.

The long term idle fuel trim is also a percentage correction of the reference load for fuel injection. So if it is -1% that means that the car wants 1% less fuel at idle. To adjust this change the injector latency map. The latency map is in ms, not ms/% like injector scale. To convert the percent fuel trim into a ms value you have to multiply by the fuel injector scale. You take the fuel injector scale in ms/% times the long term idle fuel trim in % and that gives you the long term idle fuel trim in ms. Then you use that value and either add it or subtract it from your injector latency map.

Keep repeating the test drives and tweaking of the injector scale and injector latency until the long term trims are sufficiently close to zero.

Hope that helps. Smiley

Are you doing most of this tuning with TVUB or are you doing these changes to TVTSPEV and FRLFSDP as well?
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'01.5 Audi S4 2.7T - 6MT - K04s - ASP 85mm Hitachi - 49lb Delphi
janne
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« Reply #53 on: February 02, 2011, 01:18:24 PM »

Hi all.
I tune 1.8 t (auq) seat leon whit franken hybrid turbo, 3inch s3 maf and siemens deka 630cc.
Maf calibration was easy because I copy maf calib from s3 sw.
Then I calculate needed krkte and I got 0.048396 and I use 0.000111 factor.
Then I look tvub and I put 1.14 ms like siemens data says.
Car idling bad and lamda adaptation was -25%.
Now I have 0.043956 krkte and tvub is 0.613ms car works ok and fuel adaptation is -1.2%.
Car is ok but why I have to put erong values?
my tvub factor is  0.002667.
Fuel pressure is stock and all hoses etc are ok and new maf.
Thanks for help.
Regards: janne
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Tony@NefMoto
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« Reply #54 on: February 02, 2011, 02:33:52 PM »

Was it the long term idle adaptation or the long term partial load adaptation that was off?
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janne
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« Reply #55 on: February 02, 2011, 11:45:08 PM »

Short term idle adaptation, channel 33 if i remember right.
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Tony@NefMoto
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« Reply #56 on: February 03, 2011, 03:29:01 PM »

You will want to read measuring block 32 to see your long term fuel trims.

The short term fuel trims in block 33 can fluctuate a lot, and they don't show you want the ECU has learned.

If the problem is at idle though, and not at partial load, then your problem is with the injector latency values. These can be effected by fuel pressure, voltage, age, etc.
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janne
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« Reply #57 on: February 03, 2011, 11:57:48 PM »

But if your setup is  far away lamda is always -25 or +25 and long time adaptation dont work.

Is siemensa deka latensy 1.14@14v?
Someone says it is fast and someone says it is slow, but siemens says that it is 1.14msek but it does not work on that latency Huh?
regards janne
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Tony@NefMoto
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« Reply #58 on: February 04, 2011, 05:23:43 PM »

If you are getting an adaptation of -25% at idle, and not at partial load, then you need to reduce the latency times.
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